Treatment of ores and metallurgical products



Patented Feb.22, 192v.

UNITED, STATES PATENT, osrica.

ramnar'cn 'Jomnmsnu, or GLAUSTHAL-ON-THE-HARZ, GERMANY, assrenoa r0 ramp. nun eausonwuax ax'rmnensnrrscnarr, or maennnnae-nucnu,

GERMANY.

murmur or oars Am) mn'rannuaercar. rnonucrs.

1T0 Drawing. Application Med December 6, 1924, Serial No. 754,488, and in Germany December 7, 1 923.

This invention relates to the treatment of ores and metallurgical products and residues of various kinds, and has particular reference to the volatilization therefrom ofv volatilizable metals, such as zinc, tin, lead, cadmium, arsenic, antimony and bismuth, and their recovery in the form of oxides.

Large quantities of suchores and products, such as poor-calamine and galena ores,

lowgrade brass, hard zinc and furnace sweepings and waste products, are not suitable for the'direct-production of zinc owing to the small quantity of zinc which they-contain or on account of their foreign constituents, so that recourse must be had to the roductionof oxides as an intermediate pro not. There are also certain iron ores, such as bog iron ore, and burnt out pyrites, which are rendered lowgrade by the zinc .which they contain.

The treatment of such materials in a furnace in an oxidizing atmosphere, which is produced by a heating flame with excess of air, is well known (see Patent No. 959,924, Dedolph, May 31, 1910), fusion of the material taking place when this method of treatment is employed. The disadvantage of this method of treatment however is that volatilization takes place to a reduced extemperature. In this method of treatment tent only from the very commencement of the fusion.

It has also been proposed (see Patent No. 1,269,110, Ohlmer, June 11, 1918) to introduce the material mixed with reducing substances-into a rotary furnace, and at the same time subject it to the action of a reducing flame or reducing gases at a suitable however a considerable excess of heat and energy has to be ex ended.

this and other to cause the process to be maintained continuously. As the temperature of the mass does not rise 'to the fusion point during the reaction, the mass remains in a pulverulent or clinkeriid state and .is not fused or smelted during the volatilization of the metal. a 1 1 If for example a zinc-containing material of the kind above referred to be introduced mixed with any desired fuel in a solid condition, into a rotary furnace, the material gbecomes highly heated, as its external surface is continually changing and oxidizes vigorously while the material is rolled -escape and the gases formed in t e reduction burn with evolution of heat as soon as .they issue. from the layer of material, and

the products of the combustion of the metals are recovered 'from the waste gases in the form of oxidized compounds by well known methods. By means of the present inven-' tion the entire process is simplified and also cheapened by the considerable reduction which it effects in the consumption of fuel whilst at the same time complete oxidation in the reaction zoneis ensured.

The complete oxidation of the, metal vapors and the gaseous products of reduction'being thus ensured, the heat generated thereby is utilized in the reduction zone to maintain the endothermic reduction reaction which is there proceeding to an extent which has not been possible with methods heretofore employed. y

In certain cases it is advisable to provide' a temporary or permanent, direct or indirect, heating to sup lenient if necessary the heating furnished y combustion of the metal fume and reduction gases (for example carbon monoxide).

Such additional heating is temporarily used at the outset of the operation to initiate the reducing reaction which may in many cases continue thereafter without additional heating. In other cases some additional heating bly flame or otherwise may be required.- n all cases, however, the reducing and volatilizing o eration is efiected without the fusion of t e material. In the main however the quantity of. fuel requ1red for the entire process must be provided by the amount of fuel mixed with the material treated. Another advantage which the new process also ossesses is that lowgrade fuels such as coal? dust, crude lignite and coke breeze can be used.

The following are examples'of the manner at the rate of 2500 kg. per hour. The furnace was provided at the exit end with an oil burner by which the furnace could be heated at the beginning of the run to a bright red heat. Th1s burner was in the next few hours kept going. only at adiminished rateuntil ,the furnace heat reached the desired temperature. In the further operation this additional firing was not necessary, so that 1t was omitted. The heating of the metal vapors and reduction gases burningin the oxi dizing furnace atmosphere completely sufficed for keeping up the operation and for preheating the charge. The oxides and ox- -1de combinations of volatilized metal were collected from the gases in a Cottrcll precipita'tor and recovered.

a As a second example calamine ores may be Worked in a similar manner. Since these ores usually contain considerable calcium carbonate and are damp, the water must be vaporized in the beginning of the process and the'CO driven off. The operation is as v follows:the finely divided ore in the form of a slurry is mixed with an excess of carbon, for. example 25%, and delivered to the furnace just as in example 1, and after it has been'broughtto the roper temperature in the furnace, metal vo atilization takes place in the central portion of the furnace, while at the exit end only a combustion of the excess carbon takes place, so that thecombustion gases of this excess carbon furnish additional heat for the process.

In the reaction zone a temperature of about 1000 C. to 1300 C., which is below the meltin point of thematerial, should be maintaine so as to eifect a good recovery of zinc from the material. The zinc vapors and carbon monoxide pass out from the con tinually rotating la er of material mixed with coke and are immediately burned in the atmosphere rich in oxygen which is prescut above said layer in the furnace, the heat thus produced being utilized for the reduction of the metalliferous material contained in the layer of material under treatment. The result which is practically obtained in this way is that the strongl endothermic reduction of the zinc oxide ZnO) is compensated by the heat of formation of the ox ide which-is again I produced. To balance unavoidable losses of heat and to maintain the requisite temperature in the furnace,

as also to compensate for heat losses in the waste gases and by radiation, the quantity of reducing material employed is such that the process can be continuously carried on without any other source of heat, so that the process becomes essentially a selfsnstaining one so far as heat requirements are concerned. Towards the exit end of the furnace the residue cools off while at the same time preheating the air. The process is started by means of auxiliary heating.

The residue is obtained in pulverulen't form. The iron content of the core is in the residue in the form of magnetic oxide or metallic iron and can be recovered in the'usual way.

Asa third example, the process may be applied to the .resldues from zinc retorts which contain besides slag particles 15% zinc and 30% carbon. An addition of further carbonaceous material is not necessary. In this case, it is desirable to furnish from time to time additional heat because of the diflicultly c'ombu'stiblecharacter of the carbon in these residues, and because of the small content of zinc. y

In all these examples, there remains in the residues only about 1% or less of zinc, so that in these processesthere is a recovery of 95% or better of the zinc in the material treated.

The examples given above illustrate the many uses to which the process according to the present invention can be applied, but it will be understood. that it is also applicable 'to the treatment of other materials containingvolatilizable metals or compounds thereof.

The accompanying drawing shows diagrammatically an apparatus for carrying out the process.

Referring to this drawing, A- is a rotary kiln of the usual type, which in practice may be eO-meters long and 2 meters in diameter. The charge to be treated is fed into the furnace through the chute B. The gaseous and vaporized products from the furnace pass out through the flue G into any suitable collecting device such as a Cottrell recipitator or bag house. At the lower end of the inclined rotary furnace is provided a hood D provided with an opening E for the admission of air. The residual products are discharged through a chute F at the lower por tion of the hood into any suitable receptacle, such as a car G. H is an oil or gas burner, the flame of which is used to start the process, or as a -supplementary source of heat which may from time to time be required.

- in what manner the same is to be per ducing agentinto a heated metallurgicalfur- Having now particularly described and ascertained the nature of my said invention formed, I declare that what I claim isi 1. The continuous process of recovering volatilizable metal or metals -from ores, metallurgical roducts and residues of vari-' 'ous kinds, wh1ch comfrises causing the ma- 1 terial to be treate to be continuously charged together with a. carbonaceous renace in which an oxidizing atmosphere is maintained, and to travel therethrough in a constantly rolled round layer, and burning the volatilized metals and combustible gases in contact withthe charge whereby the charge is sufiicientl heated to cause continued reduction an volatilization, without slagging or fusion of the charge in the 're-' duction zone.

2. A process as claimed in claim 1 m whlch the amount of carbonaceous fuel mixed with the charge is sufiicient' to effect the reduction of the volatilized metals and to suppl by its combustion additional heat.-

3. X process as claimed in claim 1 in fication is signed.

which additional heat is applied to the charge. e j

4. The continuous process of recovering volatilizable metal or metals from ores,

metallurgical products and residues of variouskinds which comrises causing the ma-.

burning; the ,volatilizable metals and combustible gases in contact with the charge whereby the charge is sufficiently heated to cause'continued reduction and volatilization,

supplying additional heat when necessary to t e' charge,'the conditions bein so controlled that slagging or fusion of t e in the reduction zone is avoided.

In testimony whereof-the foregoing specicharge FRIEDRICH JOHANNSEN,"

Certificate of Correction.

Patent. No. 1,618,204, Granted Febnuary 22, 1927, w FRIEDRICH JOHANNSEN.

y certified that error appears in the abovernumber'ed correction as follows: The drawin It is hereb fitent requiring g containing the figure as shown low should be inserted as part of the Letters Patent:

Feb. 22, 1927.

FI JOHANNSEN TRBATFIENT OF ORBS AND IETALLURGIGAL PRODUCTS 'l-iled 'Deo 6. 1924 f M 1' 4, a :7 Z

g mu

v i I flmum Patent'should be reeid with this correction therein that the record of the case in the Patent Office. sealed this 28th day of June, A.-D. 1927.

and that the said Letters n M. J.YMO ORE," Acting Comm'ssiomr of Pqtents. 

